Additional-information detection processing apparatus and method, content playback processing apparatus and method, and computer program

ABSTRACT

Information capable of tracing a content distribution route, such as a user ID of a content destination, a content ID, a content provider ID, and a service provider ID, is superimposed on the content as additional information for digital watermarking or steganography before delivering the content. For example, the content ID and the user ID are detected from the delivered content. When both the content ID and the user ID are not detected from the content, it is determined that the content is illegally distributed, and the content distribution route is traced to identify the source of the illegally distributed content. In most cases, unique information, such as a user ID, still remains in copies of the content, thus effectively preventing illegal distribution of the content.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention The present invention relates to anadditional-information detection processing apparatus and method, acontent playback processing apparatus and method, and a computerprogram. More specifically, the present invention relates to anadditional-information detection processing apparatus and method, acontent playback processing apparatus and method, and a computer programin which the distribution of illegal content, such as copy data ofcontent data, can be effectively prevented.

[0002] 2. Description of the Related Art

[0003] With the progress of digital technology, the dissemination ofdigital recording and playback apparatuses capable of recording andplaying back many times without degradation in image or sound qualityhas increased, and a variety of digital content such as images and musiccan be delivered and distributed via media such as digital video taperecorders (VTRs), digital versatile discs (DVDs), and compact discs(CDs), or over networks.

[0004] In a known method, various types of information, such as contentcopyright information, content modification information, contentconfiguration information, content processing information, contentediting information, content playback processing schemes, and contentcopy control information, is embedded into the content as additionalinformation corresponding to the content using a digital watermark (WM)technique. Digital watermarks are typically invisible or imperceptibleon played back content (image data or audio data), and can be detectedor embedded only by executing a specific algorithm or by a specificdevice. Content is processed in a receiver, a recording and playbackapparatus, or the like to detect a digital watermark to control thecontent according to the digital watermark, thus achieving highlyreliable control.

[0005] A variety of methods of embedding and detecting digitalwatermarks in and from data have been proposed. A typical method ofembedding and detecting digital watermarks is based on the statisticalcharacteristics of original signal data such as an image. A descriptionis now given of a method of embedding a digital watermark as a basicpattern of random-number data of a PN (pseudo-noise) sequence based onthe statistical characteristics of an image signal such as a digitalvideo signal. For simplification, it is assumed herein that frame dataof a luminance signal has eight horizontal pixels by six verticalpixels.

[0006] First, PN-sequence random-number data PN is defined as follows:$\begin{matrix}{{PN} = \begin{pmatrix}{+ 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {+ 1} & {- 1} & {- 1} \\{+ 1} & {+ 1} & {- 1} & {- 1} & {- 1} & {+ 1} & {- 1} & {+ 1} \\{- 1} & {+ 1} & {+ 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {+ 1} \\{+ 1} & {- 1} & {- 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {- 1} \\{- 1} & {- 1} & {+ 1} & {+ 1} & {+ 1} & {- 1} & {- 1} & {+ 1} \\{+ 1} & {+ 1} & {- 1} & {+ 1} & {- 1} & {- 1} & {+ 1} & {- 1}\end{pmatrix}} & {{Eq}.\quad (1)}\end{matrix}$

[0007] The random-number data PN is generated so that the sum isstatistically zero. Then, embedded information DC is spread by therandom-number data PN having characteristics indicated by the aboveequation. When the polarity of the embedded information DC is expressedby “1”, the pattern of the random-number data PN is used without change.Then, the digital watermark pattern WM is expressed as follows:$\begin{matrix}{{WM} = {{PN} = \begin{pmatrix}{+ 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {+ 1} & {- 1} & {- 1} \\{+ 1} & {+ 1} & {- 1} & {- 1} & {- 1} & {+ 1} & {- 1} & {+ 1} \\{- 1} & {+ 1} & {+ 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {+ 1} \\{+ 1} & {- 1} & {- 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {- 1} \\{- 1} & {- 1} & {+ 1} & {+ 1} & {+ 1} & {- 1} & {- 1} & {+ 1} \\{+ 1} & {+ 1} & {- 1} & {+ 1} & {- 1} & {- 1} & {+ 1} & {- 1}\end{pmatrix}}} & {{Eq}.\quad (2)}\end{matrix}$

[0008] When the polarity of the embedded information DC is expressed by“0”, the inverse pattern of the random-number data PN is used. That is,the digital watermark pattern WM is expressed as follows:$\begin{matrix}{{WM} = {{- {PN}} = \begin{pmatrix}{- 1} & {+ 1} & {- 1} & {- 1} & {+ 1} & {- 1} & {+ 1} & {+ 1} \\{- 1} & {- 1} & {+ 1} & {+ 1} & {+ 1} & {- 1} & {+ 1} & {- 1} \\{+ 1} & {- 1} & {- 1} & {+ 1} & {- 1} & {- 1} & {+ 1} & {- 1} \\{- 1} & {+ 1} & {+ 1} & {+ 1} & {- 1} & {- 1} & {+ 1} & {+ 1} \\{+ 1} & {+ 1} & {- 1} & {- 1} & {- 1} & {+ 1} & {+ 1} & {- 1} \\{- 1} & {- 1} & {+ 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {+ 1}\end{pmatrix}}} & {{Eq}.\quad (3)}\end{matrix}$

[0009] If the embedded information DC is formed of a plurality ofinformation bits, the frame data of the luminance signal may be dividedinto appropriate small regions so that each of the information bits ismade to correspond with each of the regions. Alternatively, for example,a plurality of different orthogonal digital watermark patterns may beused so that each of the information bits is made to correspond witheach of the digital watermark patterns. A combination of these methodsmay also be used.

[0010] In an image signal such as a digital video signal, it is assumedthat frame data DV1 indicating a luminance signal pixel value of certainframe data is expressed as follows: $\begin{matrix}{{DV1} = \begin{pmatrix}50 & 51 & 52 & 54 & 52 & 52 & 50 & 49 \\49 & 50 & 51 & 53 & 54 & 53 & 50 & 50 \\48 & 50 & 50 & 50 & 51 & 52 & 49 & 48 \\49 & 49 & 50 & 48 & 49 & 50 & 50 & 49 \\48 & 48 & 50 & 49 & 47 & 50 & 52 & 50 \\49 & 50 & 52 & 51 & 51 & 52 & 55 & 53\end{pmatrix}} & {{Eq}.\quad (4)}\end{matrix}$

[0011] Since image signal such as digital video signals have acharacteristic that adjacent luminance signals have almost the samepixel values, the values of adjacent pixels are set herein toapproximately equal values.

[0012] The digital watermark is embedded by adding the digital watermarkpattern WM to the frame data DV1 of the luminance signal. When thepolarity of the embedded information DC is expressed by “1”, the digitalwatermark pattern WM expressed by Eq. (2) is added to the luminancesignal expressed by Eq. (4), and frame data DV2 of thedigital-watermarked luminance signal is expressed as follows:$\begin{matrix}{{DV2} = {{{DV1} + {WM}} = \begin{pmatrix}51 & 50 & 53 & 55 & 51 & 53 & 49 & 48 \\50 & 51 & 50 & 52 & 53 & 54 & 49 & 51 \\47 & 51 & 51 & 49 & 52 & 53 & 48 & 49 \\50 & 48 & 49 & 47 & 50 & 51 & 49 & 48 \\47 & 47 & 51 & 50 & 48 & 49 & 51 & 51 \\50 & 51 & 51 & 52 & 50 & 51 & 56 & 52\end{pmatrix}}} & {{Eq}.\quad (5)}\end{matrix}$

[0013] In order to detect the embedded information DC from the framedata DV2 of the digital-watermarked luminance signal, the samePN-sequence random-number data PN used for embedding the information isused. The inner product P1 of the frame data DV1 of the originalluminance signal and the random-number data PN is given by the followingequation:

P1=DV1·PN=1  Eq. (6)

[0014] With the statistical characteristics of the image signal, theinner product P1 has a value close to zero. On the other hand, the innerproduct P2 of the frame data DV2 of the digital-watermarked luminancesignal and the random-number data PN is given by the following equationwhen the polarity of the embedded information DC is expressed by “1”:$\begin{matrix}\begin{matrix}{{P2} = {{DV2} \cdot {PN}}} \\{= {\left( {{DV1} + {WM}} \right) \cdot {PN}}} \\{= {\left( {{DV1} + {PN}} \right) \cdot {PN}}} \\{= {{P1} + {PN}^{2}}} \\{= {1 + 48}}\end{matrix} & {{Eq}.\quad (7)}\end{matrix}$

[0015] When the polarity of the embedded information DC is expressed by“0”, the inner product P2 is given by the following equation:$\begin{matrix}\begin{matrix}{{P2} = {{DV2} \cdot {PN}}} \\{= {\left( {{DV1} + {WM}} \right) \cdot {PN}}} \\{= {\left( {{DV1} - {PN}} \right) \cdot {PN}}} \\{= {{P1} - {PN}^{2}}} \\{= {1 - 48}}\end{matrix} & {{Eq}.\quad (8)}\end{matrix}$

[0016] In this case, the absolute value of the inner product P2 is closeto the inner product PN² of the random-number data PN by itself. Whenthe inner product P1 of the frame data DV1 of the original luminancesignal and the random-number data PN, and the inner product P2 of theframe data DV2 of the digital-watermarked luminance signal and therandom-number data PN are calculated with respect to various images, thedistribution of the inner products P1 and P2 can be expressed using aprobability density function shown in FIG. 15. A certain nonnegativethreshold TH is set so as to discriminate portions with and withoutdigital watermarks and to determine the polarity as follows: P2 ≦ −TH:watermarked portion (polarity: 0) |P2| < TH: unwatermarked portion P2 ≧TH: watermarked portion (polarity: 1) . . . Ex. (9)

[0017] Accordingly, the embedded information DC can be detected from theframe data DV2 of the digital-watermarked luminance signal.

[0018] In practice, important points of digital watermarking are thereliability of digital watermark detection and the influence of digitalwatermarks on the image quality. In order to correctly discriminateportions with and without digital watermarks, it is necessary to definethe threshold TH so that, in FIG. 15, the probability density functioncan be accurately separated into the “watermarked” portions and the“unwatermarked” portion. Actually, however, troughs overlap in theprobability density function, and it is difficult to select thethreshold TH so as to correctly discriminate portions with and withoutdigital watermarks. The probability that an unwatermarked portion willbe considered as a “watermarked” portion is referred to as “falsepositive”. An extremely small false positive value is required forensuring secure distribution of content. In order to increase thereliability of digital watermark detection, therefore, the digitalwatermark embedding strength should be increased using a nonnegativescalar quantity C. Frame data DV2 of a luminance signal into which thedigital watermark is embedded using the scalar quantity C with a largedigital watermark embedding strength is given by the following equation:

DV2=DV1+CWM  Eq. (10)

[0019] The inner product P2 of the frame data DV2 of thedigital-watermarked luminance signal and the random-number data PNshould be much larger. More specifically, the frame data DV2 is given bythe following equation: $\begin{matrix}\begin{matrix}{{P2} = {{DV2} \cdot {PN}}} \\{= {\left( {{DV1} + {CWM}} \right) \cdot {PN}}} \\{= {\left( {{DV1} \pm {PN}} \right) \cdot {PN}}} \\{= {{P1} \pm {CPN}^{2}}}\end{matrix} & {{Eq}.\quad (11)}\end{matrix}$

[0020] However, in the case where the digital watermark embeddingstrength is increased in this way, the influence of the digitalwatermark on the image quality is not negligible. There is a tradeoffbetween the reliability of digital watermark detection and the influenceof the digital watermark on the image quality.

[0021] Techniques which effectively use human visual characteristics toembed a digital watermark have been proposed in order to reduce theinfluence of digital watermarks on the image quality as much as possiblewhile maintaining high reliability of digital watermark detection. Insuch techniques, in view of the human visual characteristics, digitalwatermark patterns are reallocated in an image, or digital watermarkpatterns are matched with the motion of an image, thus effectivelyreducing the influence of the digital watermark on the image qualitywithout changing the overall embedding strength. The human eye issensitive to changes in low-frequency regions such as flat portions, butis insensitive to changes in high-frequency regions such as edgeportions. By making use of this characteristic, digital watermarkpatterns are reallocated to imperceptible edge portions from perceptibleflat portions, thus reducing the influence of the digital watermark onthe image quality while maintaining high reliability of digitalwatermark detection. The digital watermark patterns are stationary in astill image, and the digital watermark patterns move together withmoving images, thus achieving embedding of the digital watermark in amanner imperceptible to the human eye.

[0022] Techniques of directly superimposing additional information on anoriginal information signal of image data, audio data, and so on, suchas digital watermarking, provide a strong resistance to tampering. Suchtechniques are therefore expected to be secure information addingapproaches.

[0023] In one specific digital watermarking method, for example,information such as a content ID for identifying content to be deliveredon a network, or a user ID for identifying a user to which the contentis directed is added to the content using digital watermarking beforedelivering the digitally watermarked content.

[0024] However, there has been a problem that, when the same content isassigned with different IDs for different users, a coalition of userscan detect the IDs from the differences between a plurality of pieces ofcontent and can perform signal processing to delete the IDs from thecontent so as to make the identification information undetectable,resulting in unauthorized secondary distribution of the content with theuser IDs removed therefrom. In this situation, if content containing noID originally is concurrently distributed, it is very difficult toidentify tampered content.

[0025] If there are users having such tampered content, it is alsodifficult to identify the tamperer only by analyzing the content. In acase where content to be protected is illegally distributed,illegal-content searching such as content distribution route tracing orsource finding is almost impossible, thus making it difficult to provethe illegality. Therefore, it is difficult to take appropriate actionagainst tampered content.

SUMMARY OF THE INVENTION

[0026] Accordingly, in view of the aforementioned problems with therelated art, it is an object of the present invention to provide anadditional-information detection processing apparatus and method, acontent playback processing apparatus and method, and a computer programin which the source of illegal signal processing performed on content inwhich additional information such as a digital watermark is embedded orillegal signal processing performed on the additional information can beeasily identified, thereby effectively preventing illegal contentdistribution.

[0027] In one aspect of the present invention, an additional-informationdetection processing apparatus for detecting additional information fromcontent having the additional information superimposed thereon to detectwhether or the content is illegal includes an additional-informationdetector for receiving the content and for detecting first additionalinformation, which includes content routing information; a deliveryrecord table in which content routing information of the content isrecorded; and a data verifier for comparing and verifying the firstadditional information detected by the additional-information detectorwith the content routing information recorded in the delivery recordtable. Based on a data verification result obtained by the dataverifier, the illegality of the content is detected.

[0028] The additional information may be digital watermark information,and the additional-information detector may detect the digital watermarkinformation.

[0029] The first additional information may include identificationinformation (user ID) of a user who receives the content.

[0030] The first additional information may include contentidentification information (content ID) unique to the content.

[0031] The first additional information may include service provideridentification information (service provider ID) unique to a serviceprovider, which is an entity handling content, delivery, ordistribution.

[0032] The delivery record table may include a correspondence between acontent identifier, an identifier of a user who receives the content,and an identifier of a service provider, which is an entity handlingcontent, delivery, or distribution.

[0033] The additional information may be steganography information, andthe additional-information detector may detect the steganographyinformation.

[0034] In a second aspect of the present invention, anadditional-information detection processing apparatus for detectingadditional information from content having the additional informationembedded therein in advance to detect whether or not the content isillegal includes a receiver for receiving the content; a first detectorfor detecting from the content a content ID for identifying the content;a second detector for detecting from the content a user ID foridentifying a user of the content; and a reporting unit for determiningthat the content is illegal when only one of the content ID and the userID is detected, and for reporting the illegality of the content.

[0035] The additional-information detection processing apparatus mayfurther include a content delivery record table in which content routinginformation is recorded; and a data verifier for comparing and verifyingthe content ID detected by the first detector and the user ID detectedby the second detector with the content routing information recorded inthe content delivery record table. The reporting unit may report thedetermination that the content is illegal based on a data verificationresult of the data verifier.

[0036] The content delivery record table may include a correspondencebetween a content identifier, an identifier of a user who receives thecontent, and an identifier of a service provider, which is an entityhandling content, delivery, or distribution.

[0037] In a third aspect of the present invention, a content playbackprocessing apparatus for playing back content includes anadditional-information detector for receiving content having additionalinformation superimposed thereon and for detecting a user identifier(ID) which is contained in the additional information; a memory forstoring a user identifier (ID); a comparator/verifier for comparing andverifying the user ID detected from the content with the user ID storedin the memory; and a playback controller for playing back the content onthe condition that the comparator/verifier determines that both user TDsare verified with each other.

[0038] In a fourth aspect of the present invention, anadditional-information detection processing method for detectingadditional information from content having the additional informationsuperimposed thereon to detect whether or not the content is illegalincludes an additional-information detecting step of receiving thecontent and detecting first additional information, which includescontent routing information; and a data verifying step of comparing andverifying the detected first additional information with content routinginformation of the content, which is recorded in a delivery recordtable. Based on a data verification result obtained in the dataverifying step, the illegality of the content is detected.

[0039] The additional information may be digital watermark information,and, in the additional-information detecting step, the digital watermarkinformation may be detected.

[0040] The first additional information may include identificationinformation (user ID) of a user who receives the content.

[0041] The first additional information may include contentidentification information (content ID) unique to the content.

[0042] The first additional information may include service provideridentification information (service provider ID) unique to a serviceprovider, which is an entity handling content, delivery, ordistribution.

[0043] The delivery record table may include a correspondence between acontent identifier, an identifier of a user who receives the content,and an identifier of a service provider, which is an entity handlingcontent, delivery, or distribution.

[0044] The additional information may be steganography information, and,in the additional-information detecting step, the steganographyinformation may be detected.

[0045] In a fifth aspect of the present invention, anadditional-information detection processing method for detectingadditional information from content having the additional informationembedded therein in advance to detect whether or not the content isillegal includes a content receiving step of receiving the content; afirst detecting step of detecting from the content a content ID foridentifying the content; a second detecting step of detecting from thecontent a user ID for identifying a user of the content; and a reportingstep of determining that the content is illegal when only one of thecontent ID and the user ID is detected, and reporting the illegality ofthe content.

[0046] The additional-information detection processing method mayfurther include a data verifying step of comparing and verifying thecontent ID detected in the first detecting step and the user ID detectedin the second detecting step with content routing information recordedin a content delivery record table. In the reporting step, based on adata verification result obtained in the data verifying step, thedetermination that the content is illegal may be reported.

[0047] The content delivery record table may include a correspondencebetween a content identifier, an identifier of a user who receives thecontent, and an identifier of a service provider, which is an entityhandling content, delivery, or distribution.

[0048] In a sixth aspect of the present invention, a content playbackprocessing method for playing back content includes anadditional-information detecting step of receiving content havingadditional information superimposed thereon and detecting a useridentifier (ID) which is contained in the additional information; acomparing and verifying step of comparing and verifying the user IDdetected from the content with a user identifier (ID) read from amemory; and a playback control step of playing back the content on thecondition that it is determined in the comparing and verifying step thatboth user IDs are verified with each other.

[0049] In a seventh aspect of the present invention, a computer programfor executing an additional-information detecting process for detectingadditional information from content having the additional informationsuperimposed thereon to detect whether or not the content is illegalincludes an additional-information detecting step of receiving thecontent and detecting firs additional information, which includescontent routing information; and a data verifying step of comparing andverifying the first additional information detected in theadditional-information detecting step with content routing informationof the content, which is recorded in a content delivery record table.

[0050] In an eighth aspect of the present invention, a computer programfor executing a process for detecting additional information fromcontent having the additional information embedded therein in advance todetect whether or not the content is illegal includes a contentreceiving step of receiving the content; a first detecting step ofdetecting from the content a content ID for identifying the content; asecond detecting step of detecting from the content a user ID foridentifying a user of the content; and a reporting step of determiningthat the content is illegal when only one of the content ID and the userID is detected, and reporting the illegality of the content.

[0051] In a ninth aspect of the present invention, a computer programfor executing a content playback process includes anadditional-information detecting step of receiving content havingadditional information superimposed thereon and detecting a useridentifier (ID) which is contained in the additional information; acomparing and verifying step of comparing and verifying the user IDdetected from the content with a user identifier (ID) read from amemory; and a playback control step of playing back the content on thecondition that it is determined in the comparing and verifying step thatthe user IDs are verified.

[0052] According to the present invention, therefore, informationcapable of tracing a content distribution route, such as a user ID of acontent destination, a content ID, a content provider ID, and a serviceprovider ID, is superimposed on the content as additional informationfor digital watermarking, steganography, or the like. For example, thecontent ID and the user ID are detected. When at least one of thecontent ID and the user ID is not detected, it is determined that thecontent is illegal. If the content is illegally distributed, the contentdistribution route can be traced to identify the source of the illegallydistributed content based on the additional information detected fromthe content.

[0053] According to the present invention, furthermore, a plurality oftypes of information capable of tracing a content distribution route,such as a user ID of a content destination, a content ID, a contentprovider ID, and a service provider ID, are superimposed on the content.If someone desires to delete digital watermarks without authorization,for example, if he/she collects a large amount of content image data inorder to remove common additional information, it is difficult to removeadditional information, such as a user ID, different for differentpieces of content. Since unique information such as a user ID stillremains in copies of the content, illegal distribution of the contentcan be effectively prevented.

[0054] According to the present invention, furthermore, content isplayed back only when the user ID stored in a memory of a playbackapparatus and the user ID added to the content are verified with eachother. Therefore, playback of the content is permitted only on anauthorized user's device which has received the legally deliveredcontent, while, for example, playback of a copy of the content would notbe permitted on another user's device, thus preventing illegal use ofthe content.

[0055] The computer program according to the present invention may beoffered by storage media for loading it in the computer-readable formto, for example, a general-purpose computer system capable of executingvarious program codes, such as recording media including CDs, FDs, andMO (magneto-optical) discs, or via communication media such as networks.Since the program is offered in the computer-readable form, processingfor the program can be performed on the computer system.

[0056] Other objects, features, and advantages of the present inventionwill become apparent from the following embodiments of the presentinvention and the accompanying drawings. As used herein, the term“system” represents a logical group of apparatuses, and is not limitedto one in which apparatuses with different structures are accommodatedin the same case.

BRIEF DESCRIPTION OF THE DRAWINGS

[0057]FIGS. 1A and 1B are schematic diagrams showing digitalwatermarking and steganography techniques, respectively;

[0058]FIG. 2 is a block diagram of an additional-informationsuperimposing apparatus for embedding additional information accordingto the present invention;

[0059]FIG. 3 is a block diagram of a content delivery system of thepresent invention;

[0060]FIG. 4 is a view showing the structure of motion-image data to beprocessed in an additional-information detecting process of the presentinvention;

[0061]FIG. 5 is a block diagram showing in detail a modulating processorof the additional-information superimposing apparatus;

[0062]FIGS. 6A through 6D are spectra showing spread spectrum modulationin an additional information superimposing process;

[0063]FIG. 7 is a schematic diagram showing a multi-bit informationsuperimposing process in the additional-information superimposingprocess;

[0064]FIG. 8 is a diagram showing a multi-bit information superimposingprocess in the additional-information superimposing process;

[0065]FIG. 9 is a diagram showing an example of information superimposedon the content in the additional-information superimposing process;

[0066]FIG. 10 is a block diagram of an additional-information detectionprocessing apparatus of the present invention;

[0067]FIG. 11 is a view showing an exemplary delivery record table ofthe additional-information detection processing apparatus of the presentinvention;

[0068]FIG. 12 is a block diagram of a content playback processingapparatus of the present invention;

[0069]FIG. 13 is a flowchart showing a process routine of the contentplayback processing apparatus of the present invention;

[0070]FIG. 14 is a block diagram of a system configuration of theadditional-information superimposing and detection processing apparatusand the content playback processing apparatus; and

[0071]FIG. 15 is a view showing a digital watermark embedding anddetecting process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0072] The details of an additional-information detection processingapparatus and method, and a content playback processing apparatus andmethod according to the present invention are described below withreference to the drawings.

[0073] Additional Information

[0074] First, a brief description is given of additional information tobe added to various types of information such as images and soundsaccording to the present invention. A typical example of the additionalinformation is a digital watermark (WM), as described above. As shown inFIG. 1A, for example, when information A is embedded as a digitalwatermark into an image 11, as described above in the Description of theRelated Art, the embedded information A is spread by random-number dataPN to generate a digital watermark pattern given by Eq. (3) of theDescription of the Related Art, and this pattern is embedded into theimage 11, as indicated by a pattern of the image 11 shown in FIG. 1A.

[0075] When the digital watermark is detected from the digitalwatermarked image, the same PN-sequence random-number data PN used forembedding the digital watermark is used for de-spreading. In thede-spreading operation, the inner product P1 of frame data DV1 of theoriginal luminance signal and the random-number data PN, and the innerproduct P2 of frame data DV2 of the digital-watermarked luminance signaland the random-number data PN are calculated to express the distributionof the inner products P1 and P2 using a probability density function(see FIG. 15), and a certain threshold TH is set so as to detect theembedded digital watermark information.

[0076] As described above, the digital watermark may be undetectable insome cases, for example, when digital-watermarked image data has beenencoded, such as affine-transformed. It is also difficult to detect thedigital watermark from the re-captured version of the image data.

[0077] Another type of additional information different from theabove-described digital watermark information to be embedded is used assteganography information. Steganography is a technique for hidingadditional information in images, and includes a number of methods ofdirectly superimposing a message forming additional information on animage or the like, such as a method in which data is inserted into theleast significant bit of bit information indicating each pixel value ofthe image information, invisible inks, microdots, characterrearrangement, and spread-spectrum (SS) communications.

[0078] As shown in FIG. 1B, when character information A is embeddedinto an image 12, for example, bit information of pixels of onlyportions that constitute character “A” is modified in the image 12. Forexample, the value of pixels of the portions that constitute thecharacter is modified to the current pixel value plus one. This processis performed on, for example, consecutive frames of a motion image sothat the consecutive frames are subjected to integration andnormalization to extract the added information A.

[0079] In a content playback processing apparatus and method, anadditional-information superimposing apparatus and method, and anadditional-information detection processing apparatus and method of thepresent invention, additional information for both digital watermarkingand steganography is applicable.

[0080] Additional Information Superimposing Process

[0081]FIG. 2 illustrates an additional-information superimposingapparatus for embedding additional information according to the presentinvention. As shown in FIG. 2, the additional-information superimposingapparatus includes a first modulating processor 102, a firstsuperimposing processor 103, a second modulating processor 104, a secondsuperimposing processor 105, and an encoder 106. Theadditional-information superimposing apparatus superimposes additionalinformation for digital watermarking, steganography, or the like onvarious original data such as images input from information to beprocessed (hereinafter referred to as “processed information”) 101.

[0082] It is assumed herein that a plurality of types of additionalinformation are superimposed. Although the additional-informationsuperimposing apparatus shown in FIG. 2 includes two superimposingprocessors for superimposing two types of additional information, threeor more types of additional information may be superimposed. Theplurality of types of additional information include, for example, acontent identifier (content ID), a user identifier (user ID), and aservice provider identifier (SP-ID).

[0083] In the system of the present invention, for example, contentrouting information is superimposed as additional information such as adigital watermark on the content.

[0084] Specifically, content distribution over a network shown in FIG. 3is assumed. For example, when content 201 is delivered to a user A 231via a content provider 211 and a content delivery service provider 221over a network 250, desirably, a content identifier or content ID of thecontent 201, a service provider ID of the content provider 211, aservice provider ID of the content delivery service provider 221, and auser ID of the user A 231 are all added to the content. Alternatively,an identifier of an entity selected from a plurality of entities in thiscontent distribution route is added to the content.

[0085] In this example, the content delivery service provider 221 addsto the content additional information corresponding to a content ID ofthe delivered content and a user ID of a user to which the content isdelivered.

[0086] That is, the additional-information superimposing apparatus shownin FIG. 2 is incorporated in the content delivery service provider 221,and the content delivery service provider 221 adds the content ID andthe user ID to the content to be delivered.

[0087] This is merely an example, and, for example, both the contentdelivery service provider 221 and the content provider 211 may includethe additional-information superimposing apparatus, so that the contentID and the user ID are added to the content by the content provider 211and the content delivery service provider 221, respectively.

[0088] The processed information 101 includes various data such asimages, audio data, and program data into which additional informationis to be embedded, including, for example, data read from storage mediasuch as hard disks and DVDs, and images supplied from image capturingdevices such as scanners and digital cameras.

[0089] In the following description, additional information issuperimposed on image data, by way of example. However, the presentinvention is not limited to image data, and is generally applicable tovarious information signals such as audio data and other programinformation.

[0090] When additional information is superimposed on a motion image,the additional-information superimposing process is performed on everyframe image. FIG. 4 illustrates a frame structure of a motion image. Asshown in FIG. 4, when frame data forming the motion image includes asequence of frames k to k+n along a time axis t, the data is processedin turn, starting from the frame k.

[0091] In the structure shown in FIG. 2, it is assumed that firstadditional information indicates a content ID and second additionalinformation indicates a user ID. For example, the first additionalinformation and the second additional information are added as digitalwatermark or steganography information. In the following description,both the first additional information and the second additionalinformation are added as digital watermark information, by way ofexample.

[0092] In the first modulating processor 102, digital watermark (WM)information corresponding to the content ID is modulated. The firstmodulating processor 102 performs a modulation process to embed theadditional information into data, that is, to embed a digital watermarkcorresponding to bit information of the content ID into an image. Themodulation process includes, for example, spread spectrum modulation,patchwork, and so on.

[0093] The spread spectrum modulation is now described.

[0094]FIG. 5 is a block diagram of a spectrum spreading processor in thefirst modulating processor 102. In FIG. 5, a PNa generator 281 generatesa PN code string PNa, and supplies the PN code string PNa to a spectrumspreader 282.

[0095] An additional-information generator 283 generates additionalinformation (data string based on a content ID) to be superimposed asdigital watermark information, and supplies the additional informationto the spreader 282. The spreader 282 multiplies the additionalinformation by the PN code string PNa to generate a spread spectrumsignal. The spread spectrum signal is then output to a digital watermark(WM) level controller.

[0096]FIGS. 6A through 6D are spectra showing the relationship betweenadditional information to be superimposed as digital watermarkinformation and data, such as a video signal, into which the digitalwatermark is to be embedded. FIG. 6A is the spectrum of the originaladditional-information signal, FIG. 6B is the spectrum of the spreadadditional-information signal, FIG. 6C is the spectrum of the videosignal on which the spread additional-information signal issuperimposed, and FIG. 6D is the spectrum of the de-spread signal.

[0097] The additional information is a low-bit-rate signal having asmall amount of information, and is a narrow-band signal, as shown inFIG. 6A. By spreading this signal, a signal having a broader bandwidthis generated, as shown in FIG. 6B. At this time, the level of the spreadspectrum signal decreases in inverse proportion to the spreading ratioof the bandwidth.

[0098] This spread spectrum signal, i.e., the SS additional information,is superimposed on target data such as a video signal, in which case, asshown in FIG. 6C, the SS additional information is superimposed at alower level than the dynamic range of the video signal serving as theinformation signal. This substantially prevents degradation of the maininformation signal.

[0099] The signal is de-spread to detect the SS additional information.The de-spreading operation allows the SS additional information to berestored to the original narrow-band signal, as shown in FIG. 6D. Givena sufficient band spreading factor, the detection level of the de-spreadadditional information exceeds the information signal, and theadditional information can therefore be detected.

[0100] The first superimposing processor 103 superimposes the firstadditional information on the processed information (image) 101.

[0101] In the second modulating processor 104, a similar process to theprocess performed in the first modulating processor 102 is performed onthe additional information corresponding to the user ID for identifyinga user to which the content is delivered, and the modulated data issuperimposed by the second superimposing processor 105.

[0102] Both the content ID and the user ID typically comprise multi-bitinformation. The multi-bit information can be embedded into an imageusing digital watermarking by any of the following methods: using aplurality of digital watermark patterns, dividing the image into smallregions, or using a combination thereof.

[0103] In the method of using a plurality of digital watermark patterns,the following techniques are conceivable: a technique of exclusivelyembedding a plurality of digital watermark patterns with differentmeanings into an image to represent desired information, a technique ofsimultaneously embedding a plurality of overlapping digital watermarkpatterns into an image to represent desired information using acombination of the patterns, and a technique of combining these twotechniques. A process for embedding a plurality of digital watermarkpatterns into an original image is illustrated in FIG. 7.

[0104] In the example shown in FIG. 7, each of the content ID and theuser ID comprises k-bit information. A plurality of digital watermarkpatterns with different meanings associated with the respective bits areexclusively embedded into an image to represent desired information. Inthis technique, assuming that the number of bits of information to beembedded into an image is indicated by “b”, then, the number of requireddigital watermark pattern types n is given by n=2^(b). In the techniqueof simultaneously embedding a plurality of overlapping digital watermarkpatterns into an image to represent desired information using acombination of the patterns, on the other hand, the number of requireddigital watermark pattern types n is given by n=b. The latter techniquerequires fewer digital watermark pattern types, but often requiresappropriate actions against degradation in image quality caused byembedding a plurality of overlapping digital watermark patterns into theimage. Finally, the technique of combining these two techniques requiresn digital watermark pattern types given by b≦n≦2^(b), and has theadvantages of both techniques.

[0105] The method of dividing an image into small regions is anotherapproach of embedding multi-bit information into an image using digitalwatermarking. In this case, the regions are allocated different roles sothat a plurality of digital watermarks can coexist in the image. Forexample, as shown in FIG. 8, some regions of a content image are used asregions into which the content ID is to be embedded, and other differentregions are used as regions into which the user ID is to be embedded.

[0106] In this way, the first superimposing processor 103 and secondsuperimposing processor 105 of the additional-information superimposingapparatus shown in FIG. 2 are able to superimpose different types ofinformation so as not to make the information of one processorundetectable due to interference with the information of the otherprocessor.

[0107]FIG. 9 schematically illustrates content having a plurality oftypes of additional information embedded therein. A content ID 291, aservice provider ID 292, and a user ID 293 are embedded in the contentshown in FIG. 9. In FIG. 9, the additional information is indicated assymbolic or numerical information; in practice, however, the embeddedinformation, which is, for example, digital watermark information,allows a bit string to be detected based on the symbolic or numericalinformation.

[0108] The encoder 106 shown in FIG. 2 encodes the processed information(content) having a plurality of types of additional information embeddedtherein. This encoding process involves a data compression process forreducing the amount of data for network transfer or storage in a storagemedium. The data encoded with, for example, a compression scheme such asMPEG compression, is transferred over a network asadditional-information-embedded information 107 or is stored in astorage medium before being offered to a user corresponding to the userID added to the content.

[0109] Additional Information Detecting Process

[0110] A description is now given of a process for detecting additionalinformation from information on which the additional information issuperimposed by the above-noted additional-information superimposingprocess.

[0111]FIG. 10 is a block diagram of an additional-information detectionprocessing apparatus of the present invention. Theadditional-information detection processing apparatus shown in FIG. 10is a processor for detecting additional information and tracing acontent distribution route.

[0112] As shown in FIG. 10, the additional-information detectionprocessing apparatus of the present invention includes a decodingprocessor 302, a first detecting processor 303, a second detectingprocessor 304, a data verifier 305, a delivery record table 306, areporting unit 307, and a receiver 308. Additional-information-embeddedinformation 301, which is original information, is received by thereceiver 308 to detect information such as a digital watermark.

[0113] The additional-information-embedded information 301 includesvarious data such as images, audio data, and program data in whichadditional information is embedded. The receiver 308 receives contentfrom, for example, a network or content read from a storage medium, andoutputs it to the decoding processor 302.

[0114] In the following description, additional information is detectedfrom image data, by way of example. However, the present invention isnot limited to image data, and is generally applicable to variousinformation signals such as audio data and other program information.

[0115] When additional information is detected from a motion image,every frame image is processed. In FIG. 10, first additional informationand second additional information to be detected differ from each other,and may be, for example, a content ID and a user ID, respectively.

[0116] The decoding processor 302 performs a decoding processcorresponding the encoding process performed by the encoder 106 of theadditional-information superimposing apparatus shown in FIG. 2, such asa data decompression or extension process corresponding to the MPEGencoding.

[0117] The first detecting processor 303 and the second detectingprocessor 304 detect different types of additional informationcorresponding to a content ID and a user ID, and detect, for example,digital watermark information. The first and second detecting processors303 and 304 detect spread spectrum (SS) additional information byde-spreading operation for detection based on a correlation of thedigital watermark pattern.

[0118] For example, the inner product P2 of frame data of adigital-watermarked motion image and random-number data PN is calculatedto obtain a probability density function which exhibits the distributionof the inner product P2 (see FIG. 15). A certain nonnegative thresholdTH is set so as to discriminate portions with and without digitalwatermarks and to determine the polarity as follows: P2 ≦ −TH:watermarked portion (bit 0) |P2| < TH: unwatermarked portion P2 ≧ TH:watermarked portion (bit 1)

[0119] Accordingly, the content ID corresponding to the first additionalinformation and the user ID corresponding to the second additionalinformation are detected. If the content ID was detected but the user IDwas not detected, the data verifier 305 in the present inventiondetermines that, for example, the coalition attack described above inthe Description of the Related Art occurred, and determines that thecontent is illegally tampered. When the data verifier 305 detectsillegally tampered content, it reports the detection to a user via thereporting unit 307. The reporting unit 307 may use various alarmingmethods such as sound, light, or display indication for notification.

[0120] The data verifier 305 refers to the data stored in the deliveryrecord table 306 based on the detected information to determine whetheror not the content is legally distributed, and traces a contentdistribution route. If it is determined that the content is illegallydistributed, this information may be reported by, for example, thereporting unit 307 to a content manager or the like via the Internet orthe like. In this case, the reporting unit 307 has both functions ofreporting the illegal content to a user and reporting routinginformation of the illegal content to a content manager.

[0121]FIG. 11 shows a data structure of the delivery record table 306.The table shown in FIG. 11 is a table for identifying contentdistribution routes of content delivered to various users, and includesa correspondence between a content ID, a service provider ID of aplurality of content providers and content delivery service providers,and user IDs of users to which the content is delivered.

[0122] The content distribution route can be identified by verifying thetable data with additional information detected from the content, suchas a content ID and a user ID.

[0123] For example, if the content is illegally copied for secondarydistribution on a network, a plurality of pieces of content having thesame user ID exist. Then, it can be determined that the usercorresponding to the user ID or the service provider(s) on the contentdistribution route made illegal copies of the content for secondarydistribution of the illegally copied content. The delivery record table306 may be stored in a different server on a network such as theInternet, and may be referred to, if necessary, each time the dataverifier 305 accesses the server.

[0124] Content Playback Processing Apparatus

[0125] A description is now given of a process for receiving contentcontaining additional information at a user side over a network or via astorage medium and for playing back the content.

[0126]FIG. 12 is a block diagram of a content playback processingapparatus. As shown in FIG. 12, the content playback processingapparatus of the present invention includes a decoding processor 502, anadditional-information detecting processor 503, a comparator/verifier504, a user ID storage memory 505, and a playback controller 506. Thecontent playback processing apparatus receivesadditional-information-embedded information 501 to detect additionalinformation such as a digital watermark and to control content playbackbased on the detected information.

[0127] The additional-information-embedded information 501 includesvarious data such as images, audio data, and program data in whichadditional information is embedded.

[0128] In the following description, image data is played back, by wayof example. However, the present invention is not limited to image data,and is generally applicable to various information signals such as audiodata and other program information.

[0129] The decoding processor 502 performs a decoding processcorresponding to the encoding process performed by the encoder 106 ofthe additional-information superimposing apparatus shown in FIG. 2, suchas a data decompression or extension process corresponding to the MPEGencoding.

[0130] The additional-information detecting processor 503 detectsadditional information corresponding to the user ID, and detect, forexample, digital watermark information. The additional-informationdetecting processor 503 detects spread spectrum (SS) additionalinformation by de-spreading operation for detection based on acorrelation of the digital watermark pattern.

[0131] The comparator/verifier 504 verifies the detected user ID withthe user ID stored in the user ID storage memory 505. Since the user IDstored in the user ID storage memory 505 is a user ID submitted to thecontent provider, the user ID should be verified with the user ID addedas additional information to the content when the content is legallydelivered and received by an authorized user.

[0132] The comparator/verifier 504 verifies the detected user ID withthe user ID stored in the user ID storage memory 505, and outputs aplayback-enable signal to the playback controller 506 only when both areverified. When both are not verified, the playback-enable signal is notoutput.

[0133] The playback controller 506 plays back the content input from thedecoding processor 502 on the condition that the playback-enable signalis input from the comparator/verifier 504.

[0134] Since the content is played back only when the user ID stored inthe playback apparatus and the user ID added to the content are verifiedwith each other, playback of the content is permitted only on anauthorized user's device which has received the legally deliveredcontent. Therefore, for example, playback of a copy of the content wouldnot be permitted on another user's device, thus preventing illegal useof the content.

[0135]FIG. 13 is a flowchart showing a process routine of a contentplayback processing apparatus of the present invention.

[0136] First, in step S101, a decoding processor performs a decodingprocess such as a decoding process corresponding to the MPEG encoding.Then, in step S102, an additional-information detecting processordetects additional information corresponding to a user ID, and, in stepS103, a comparator/verifier verifies the detected user ID with a user IDstored in a user ID storage memory.

[0137] It is determined in step S104 whether or not both are verified.If the user ID added as additional information to the content isverified with the user ID stored in the user ID storage memory, then, instep S105, a playback-enable signal is output to a playback controller,and the content is played back in step S106.

[0138] If it is determined in step S104 that the user ID added asadditional information to the content is not verified with the user IDstored in the user ID storage memory, the routine proceeds to step S107,in which the playback-enable signal is not output to disable playback,and the routine ends.

[0139] The additional-information superimposing process, theadditional-information detecting process, and the content playbackprocess of the present invention have been described. In the foregoingdescription, a content ID and a user ID are used as an example ofinformation added to content; however, a variety of types of additionalinformation capable of tracing a content distribution route, such as auser ID of a content destination, a content ID, a content provider ID,and a service provider ID, may be superimposed. Preferably, IDs of allentities on a content distribution route are added to the content,resulting in more accurate content distribution route tracing.Information such as the time of content distribution transaction mayalso be embedded into the content using digital watermarking,steganography or the like, resulting in more detailed contentdistribution information.

[0140] According to the present invention, therefore, since a pluralityof different types of additional information capable of tracing acontent distribution route, such as a user ID of a content destination,a content ID, a content provider ID, and a service provider ID, aresuperimposed, for example, when legally distributed content is copiedwithout authorization for secondary distribution, the additionalinformation can be detected from the illegally distributed content totrace a content distribution route to identify the source of theillegally distributed content.

[0141] System Configuration

[0142] The above-described series of processes, i.e., theadditional-information embedding and detecting process, the contentplayback control process, and so on, can be implemented by hardware orsoftware, or a combination thereof. When it is implemented by software,a program in which the process sequence is recorded can be installedinto a memory of a data processor built in dedicated hardware forexecution, or the program can be installed into a general-purposecomputer capable of executing various processes for execution. When theseries of processes is implemented by software, a program constitutingthe software is installed into, for example, a general-purpose computer,a one-chip microcomputer, or the like.. FIG. 14 illustrates a systemconfiguration of an apparatus for executing the above-describedadditional-information detecting or embedding process or contentplayback control process.

[0143] A CPU (central processing unit) 802 actually executes variousapplication programs or OS (operating system). A ROM (read-only memory)803 stores the programs executed by the CPU 802 or fixed data ascomputation parameters. A RAM (random access memory) 804 is used as astorage area and a work area for a program executed by the CPU 802 andtime-varying parameters during the program processing. The CPU 802, theROM 803, the RAM 804, and a hard disk 805 are connected with each othervia a bus 801 so that data can be transferred therebetween. The data canalso be transferred from and to various input and output devicesconnected to an input/output interface 814.

[0144] A keyboard 812 and a mouse 813 are operated by a user forinputting various commands to the CPU 802, and are operated by a userfor entering command input data, which is input via a keyboard/mousecontroller 811.

[0145] A drive 809 is a drive for activating recording and playbackoperations of a removable recording medium 810 such as a flexible disc,a CD-ROM (compact disc read only memory), an MO (magneto-optical) disc,a DVD (digital versatile disc), a magnetic disc, or a semiconductormemory to play back a program or data from the removable recordingmedium 810 or to store a program or data to the removable recordingmedium 810.

[0146] When a command is input via the input/output interface 814 usingthe keyboard 812, the mouse 813, etc., the CPU 802 executes the programstored in the ROM 803 according to the input command.

[0147] Data such as images and audio data to be processed by theapparatuses of the above-described embodiment can be entered from aninput device such as a camera 8071 connected to an input unit 807 or adata input device such as a scanner, or from the removable recordingmedium 810 connected to the drive 809, such as a flexible disc, aCD-ROM, an MO disc, a DVD, a magnetic disc, or a semiconductor memory.In this system, audio data can also be input via a microphone 8072. Datareceived via a communication unit 808 can also be processed. The data,such as images and sounds, which is processed according to the presentinvention is played back by a computer device 8061 having a monitor, aspeaker 8062, or the like via an output unit 806.

[0148] The CPU 802 can load to the RAM 804 for execution a programstored in the ROM 803, a program stored in the hard disc 805, a programreceived by the communication unit 808 via a satellite or a network andinstalled into the hard disc 805, or a program read from the removablerecording medium 810 attached to the drive 809 and installed into thehard disk 805.

[0149] Throughout the specification, the program may be processed by asingle computer or may be distributed and processed by a plurality ofcomputers. The program may also be transferred to a remote computer forexecution.

[0150] The present invention has been described in detail with referenceto the specific embodiment. However, it is obvious that modifications orreplacements may also be made to the illustrated embodiment by thoseskilled in the art without departing from the scope and spirit of thepresent invention. The above embodiment of the present invention ismerely one exemplary form, and should not be construed as the restrictedone. Consequently, reference should be made to the appended claims forprecise delineation of the true scope of the present invention.

What is claimed is:
 1. An additional-information detection processingapparatus for detecting additional information from content having theadditional information superimposed thereon to detect whether or thecontent is illegal, said additional-information detection processingapparatus comprising: additional-information detecting means forreceiving the content and for detecting first additional information,which includes content routing information; a delivery record table inwhich content routing information of the content is recorded; and dataverifying means for comparing and verifying the first additionalinformation detected by said additional-information detecting means withthe content routing information recorded in said delivery record table,wherein the illegality of the content is detected based on a dataverification result obtained by said data verifying means.
 2. Anadditional-information detection processing apparatus according to claim1, wherein the additional information comprises digital watermarkinformation; and said additional-information detecting means detects thedigital watermark information.
 3. An additional-information detectionprocessing apparatus according to claim 1, wherein the first additionalinformation includes identification information of a user who receivesthe content.
 4. An additional-information detection processing apparatusaccording to claim 1, wherein the first additional information includescontent identification information unique to the content.
 5. Anadditional-information detection processing apparatus according to claim1, wherein the first additional information includes service provideridentification information unique to a service provider, which is anentity handling content, delivery, or distribution.
 6. Anadditional-information detection processing apparatus according to claim1, wherein said delivery record table includes a correspondence betweena content identifier, an identifier of a user who receives the content,and an identifier of a service provider, which is an entity handlingcontent, delivery, or distribution.
 7. An additional-informationdetection processing apparatus according to claim 1, wherein theadditional information comprises steganography information; and saidadditional-information detecting means detects the steganographyinformation.
 8. An additional-information detection processing apparatusfor detecting additional information from content having the additionalinformation embedded therein in advance to detect whether or not thecontent is illegal, said additional-information detection processingapparatus comprises: means for receiving the content; first detectingmeans for detecting from the content a content identifier foridentifying the content; second detecting means for detecting from thecontent a user identifier for identifying a user of the content; andreporting means for determining that the content is illegal when onlyone of the content identifier and the user identifier is detected, andfor reporting the illegality of the content.
 9. Anadditional-information detection processing apparatus according to claim8, further comprising: a content delivery record table in which contentrouting information is recorded; and data verifying means for comparingand verifying the content identifier detected by said first detectingmeans and the user identifier detected by said second detecting meanswith the content routing information recorded in said content deliveryrecord table, wherein said reporting means reports the determinationthat the content is illegal based on a data verification result of saiddata verifying means.
 10. An additional-information detection processingapparatus according to claim 9, wherein the content delivery recordtable includes a correspondence between a content identifier, anidentifier of a user who receives the content, and an identifier of aservice provider, which is an entity handling content, delivery, ordistribution.
 11. A content playback processing apparatus for playingback content, comprising: additional-information detecting means forreceiving content having additional information superimposed thereon andfor detecting a user identifier which is contained in the additionalinformation; a memory for storing a user identifier; comparing andverifying means for comparing and verifying the user identifier detectedfrom the content with the user identifier stored in said memory; andplayback control means for playing back the content on the conditionthat said comparing and verifying means determines that the useridentifier detected from the content and the user identifier stored insaid memory are verified with each other.
 12. An additional-informationdetection processing method for detecting additional information fromcontent having the additional information superimposed thereon to detectwhether or not the content is illegal, said additional-informationdetection processing method comprising: an additional-informationdetecting step of receiving the content and detecting first additionalinformation, which includes content routing information; and a dataverifying step of comparing and verifying the detected first additionalinformation with content routing information of the content, which isrecorded in a delivery record table, wherein the illegality of thecontent is detected based on a data verification result obtained in saiddata verifying step.
 13. An additional-information detection processingmethod according to claim 12, wherein the additional informationcomprises digital watermark information; and said additional-informationdetecting step includes detecting the digital watermark information. 14.An additional-information detection processing method according to claim12, wherein the first additional information includes identificationinformation of a user who receives the content.
 15. Anadditional-information detection processing method according to claim12, wherein the first additional information includes contentidentification information unique to the content.
 16. Anadditional-information detection processing method according to claim12, wherein the first additional information includes service provideridentification information unique to a service provider, which is anentity handling content, delivery, or distribution.
 17. Anadditional-information detection processing method according to claim12, wherein the delivery record table includes a correspondence betweena content identifier, an identifier of a user who receives the content,and an identifier of a service provider, which is an entity handlingcontent, delivery, or distribution.
 18. An additional-informationdetection processing method according to claim 12, wherein theadditional information comprises steganography information; and saidadditional-information detecting step includes detecting thesteganography information.
 19. An additional-information detectionprocessing method for detecting additional information from contenthaving the additional information embedded therein in advance to detectwhether or not the content is illegal, said additional-informationdetection processing method comprising: a content receiving step ofreceiving the content; a first detecting step of detecting from thecontent a content identifier for identifying the content; a seconddetecting step of detecting from the content a user identifier foridentifying a user of the content; and a reporting step of determiningthat the content is illegal when only one of the content identifier andthe user identifier is detected, and reporting the illegality of thecontent.
 20. An additional-information detection processing methodaccording to claim 19, further comprising: a data verifying step ofcomparing and verifying the content identifier detected in said firstdetecting step and the user identifier detected in said second detectingstep with content routing information recorded in a content deliveryrecord table, wherein said reporting step includes reporting thedetermination that the content is illegal based on a data verificationresult obtained in said data verifying step.
 21. Anadditional-information detection processing method according to claim20, wherein the content delivery record table includes a correspondencebetween a content identifier, an identifier of a user who receives thecontent, and an identifier of a service provider, which is an entityhandling content, delivery, or distribution.
 22. A content playbackprocessing method for playing back content, comprising: anadditional-information detecting step of receiving content havingadditional information superimposed thereon and detecting a useridentifier which is contained in the additional information; a comparingand verifying step of comparing and verifying the user identifierdetected from the content with a user identifier read from a memory; anda playback control step of playing back the content on the conditionthat it is determined in said comparing and verifying step that the useridentifier detected from the content and the user identifier read fromthe memory are verified with each other.
 23. A computer program forexecuting an additional-information detecting process for detectingadditional information from content having the additional informationsuperimposed thereon to detect whether or not the content is illegal,said computer program comprising: an additional-information detectingstep of receiving the content and detecting first additionalinformation, which includes content routing information; and a dataverifying step of comparing and verifying the first additionalinformation detected in said additional-information detecting step withcontent routing information of the content, which is recorded in acontent delivery record table.
 24. A computer program for executing aprocess for detecting additional information from content having theadditional information embedded therein in advance to detect whether ornot the content is illegal, said computer program comprising: a contentreceiving step of receiving the content; a first detecting step ofdetecting from the content a content identifier for identifying thecontent; a second detecting step of detecting from the content a useridentifier for identifying a user of the content; and a reporting stepof determining that the content is illegal when only one of the contentidentifier and the user identifier is detected, and reporting theillegality of the content.
 25. A computer program for executing acontent playback process, comprising: an additional-informationdetecting step of receiving content having additional informationsuperimposed thereon and detecting a user identifier which is containedin the additional information; a comparing and verifying step ofcomparing and verifying the user identifier detected from the contentwith a user identifier read from a memory; and a playback control stepof playing back the content on the condition that it is determined insaid comparing and verifying step that the user identifier detected fromthe content and the user identifier read from the memory are verifiedwith each other.